1. Field of the Invention
The present invention relates to improvements on motors, and more particularly to improvements for aligning the magnetic centers of motors.
2. Related Art
FIG. 3 shows a conventional motor. The motor includes a core support portion for a stator core 3 formed in a core holder 2, and a stator 1 accommodated therein. The core support portion is provided with a generally cylindrical core clamp face 2a positioned in the axial direction and a flat core locating face 2b perpendicular to the axial direction. The stator core 3 includes a stacked magnetic body having a plurality of magnetic plates 3a fixed to an outer peripheral surface of the core clamp face 2a. The magnetic plates 3a may be fixed by press fitting or another type of fitting method. The magnetic plates 3a, at a bottom portion of the stator core 3, abuts against the core locating face 2b while the stator core 3 is maintained in the axial direction.
On the outside of the stator core 3, there is a cupshaped rotor case 4 which is rotatably disposed to cover the stator 1 and the stator core 3. A circular driving magnet 5 is mounted on an inner circumference of the rotor case 4 and disposed in a manner so as to face salient poles.
In order to achieve a stable rotation of the rotor case 4, an attracting magnet 6 is provided on an uppermost portion of magnetic plates 3a. The attraction force of the attracting magnet 6 causes the rotor case 4 to move in the axial direction towards the stator 1. As a result of providing attracting magnet 6, the rotor case 4 rotates in such a manner that the magnetic center of the driving magnet 5 does not displace the position of the magnetic center f the stator core 3 in the axial direction. Further, the attracting magnet 6 prevents vibrations and undesired sounds created by the displacement of the magnetic center of the driving magnet 5 with respect to the magnetic center of the stator core 3.
In the embodiment described above even when the attracting magnet 6 is provided such that both magnetic centers of the driving magnet 5 and the stator core 3 are in the same position, there are times when both magnetic centers do not coincide with each other. This is because there are variations in the dimensions of the parts used. It is however, acceptable in the industry to have variations in these parts. For example, the stacked magnetic body including the stator core 3 which includes a plurality of magnetic plates 3a which are piled up in an axial direction have variations in the axial direction. Thus, it is difficult to manufacture and insure that both the magnetic centers coincide with each other with a high degree of accuracy.
Also, in the embodiment described above, dimensional errors in the axial direction of the stator core 3 occur wherein the magnetic center of the stator core 3 has been designed to be off set from the magnetic center of the driving magnet 5 by a specified distance. As a result, vibrations and undesired sounds occur.
Other features and advantages of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings that illustrate, by way of example, various features of embodiments of the present invention.
The present invention provides a motor including a stator core held on a core holder with the stator core including a stacked magnetic body having a plurality of magnetic plates with the magnetic plates being piled up in an axial direction. The motor also includes a core support portion provided in the core holder with the core support portion including a core mounting face and a core locating face. The core locating face is formed near a magnetic center of the stator core with respect to the axial direction and formed flat in the core holder in a radial direction. The stacked magnetic body is divided into two stacked magnetic bodies with a boundary position of the two stacked magnetic bodies being set near the magnetic center of the stator core and the boundary surface of one of the two stacked bodies abuts against the core locating face of the core holder in the axial direction.